1. Field of the Invention
The present invention relates to gyratory crushers and in particular to a piston and cylinder arrangement supporting the crusher head accommodating momentary displacement of the head to allow noncrushable materials to pass through the crusher.
2. Description of the Prior Art
The prior art includes a variety of gyratory crushers wherein the crusher head is supported by a hydraulic system which includes means for lowering the crusher head to allow tramp iron or other noncrushable materials to pass through the crusher.
Typically, as shown in U.S. Pat. No. 4,060,205, the main shaft of the crusher head is supported by a hydraulic piston and cylinder unit which is supplied with hydraulic fluid by a pump and accumulator which can be actuated to maintain the desired crushing gap between the crusher head and the bowl of the crusher. This type of arrangement has generally been necessary in order to compensate for wear in the surface of the crusher head during use. In the event a piece of tramp iron is fed into the crusher, the crusher head is driven down by the tramp iron which tends to jam in the crushing gap until the gap is sufficiently enlarged to allow this material to pass through the crusher. This downward movement of the crusher head effectively forces the hydraulic fluid in the unit through a conduit into the accumulator until the tramp iron passes through the gap. Thereafter, once the tramp iron has passed through the gap, the accumulator forces the fluid back through the conduit and into the unit which returns the crusher head to its normal operating position.
While tramp iron relief arrangements such as the foregoing have been for the most part satisfactory, the frictional losses inherent in any system requiring the movement of hydraulic fluids through a series of conduits necessarily retards or reduces the response time of the system. This response time, or the time required to lower the crusher head sufficiently to allow a piece of tramp iron to pass through the crushing gap, is particularly important since the longer a piece of tramp iron remains jammed in the crushing gap, the greater the likelihood of damage to the crusher head and its driving mechanism.